1. Field of the Invention
The present invention relates to an electronic flash apparatus with extendable on/off switch control apparatus and more particularly to an electronic flash apparatus having extendable on/off switch control apparatus and adapted for use with cameras wherein the switch control apparatus when extended, is in position to be engaged by the camera user's hand when holding the camera in its normally expected manner.
2. Description of the Prior Art
Electronic flash units for providing artificial illumination during photographic exposures occurring under conditions of low ambient scene light intensity are well known in the art. Such electronic flash units are generally adapted to receive an external, substantially steady state, d-c battery voltage which powers a voltage converter in a conventional manner to convert the d-c voltage which may be in the order of 6 volts, to a suitable flash operating voltage. A charging current from the voltage converter is directed to a storage capacitor so as to gradually charge the storage capacitor to a d-c voltage which may be in the order of 350 volts. Means are also provided for selectively discharging the storage capacitor through a flash discharge tube to produce the photographic illuminating flash of light. An on/off switch may also be provided to control the power connection from the battery to the voltage converter. Thus, when a photographer anticipates using the electronic flash, he must initially turn on the on/off switch to power the voltage converter and thereafter wait a short period of time for the storage capacitor to become fully charged. After the storage capacitor in the electronic flash is discharged through the flash tube during a photographic exposure operation of the camera, the voltage converter will automatically operate to recharge the storage capacitor in anticipation of a subsequent photographic exposure unless the operator consciously remembers to turn off the on/off switch. Should the operator fail to consciously turn off the on/off switch and let the camera sit idle for a period of time, the voltage converter will continue to operate to maintain the charged condition of the storage capacitor thereby providing a constant current drain on the battery. A prolonged period of idleness with the on/off switch remaining on may ultimately result in the complete drainage of the battery so as to render the battery inoperative.
One approach to solving this problem has involved the use of a time-out circuit within the electronic flash so as to automatically disconnect the battery from the voltage converter if the flash is not fired within a prescribed time period. However, such a time-out circuit generally involves the use of a power transistor in series connection between the battery and voltage converter which decreases the actual power input to the voltage converter as a result of the high power losses inherent to the power transistor.
A so called "two-button camera" having an integral flash unit built therein has been disclosed in a copending application for U.S. patent Ser. No. 570,165 entitled "Photographic Apparatus", by E. H. Land, filed Apr. 21, 1975 now U.S. Pat. No. 4,007,469 in common assignment herewith. This two-button camera embodies a so called "grip switch" in the base portion thereof to turn on the electronic control circuit associated with both the camera and the electronic flash when the camera is held by the user. However, electronic flash units are generally configured to be detachable from the top of the lens housing portion of the camera thereby making it inconvenient for a grip switch, which constitutes an integral part of the camera, to control the detachable electronic flash unit. Since the electronic flash unit is normally connected above the shutter housing of the camera, it has also heretofore been inconvenient to provide the electronic flash unit with its own grip switch since most cameras are not normally held above their shutter housings.
It is therefore a primary object of this invention to provide means for automatically turning on and off an electronic flash unit as a function of whether the camera to which the electronic flash unit is attached is held in position in anticipation of taking a photographic picture.
It is also an object of this invention to provide an electronic flash unit with extendable on/off switch control apparatus for automatically controlling the electrical connection between the electronic flash and its associated battery as a function of whether the camera to which the electronic flash is connected is held in its normally expected position in anticipation to taking a photographic picture.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the mechanism and system possessing the construction, the combination of elements and the arrangement of parts which are exemplified in the following detailed disclosure.